Universal Serial Bus (“USB”) connections are of increasing popularity in computer systems. FIG. 1 depicts a conventional computer system 10 that has USB connectors. The conventional computer system 10 could be a number of computer systems, including for example, a notebook computer or desk top computer. The conventional computer system 10 includes a host 12, a first USB connector 14, a USB hub 16, USB connectors 18 and 20 and a power supply 22. The host 12 includes the integrated circuits and, therefore, the processor (not explicitly shown) that operate the operating system (not explicitly shown) for the computer system 10. For example, the host 12 might include four INTEL™ integrated circuits. Thus, the host 12 might include INTEL™ processors which run a MICROSOFT™ operating system. The conventional computer system 10 also includes the USB connector 14. The conventional computer system 10 could include another USB connector (not explicitly shown) and operate as desired. Due to the popularity of USB connectivity, the conventional computer system 10 is desired to have a larger number of USB connectors. Consequently, the USB hub 16 that connects the host 12 to USB connectors 18 and 20 is provided. Thus, the USB hub 16 allows additional USB connectors 18 and 20 to be integrated into the computer system 10. In order to operate, the USB hub may connected to and be supplied with power from the power supply 22. Typically, the conventional computer system 10 includes the components 12, 14, 16, 18, 20 and 22 integrated into a housing.
Although the conventional computer system 10 functions, one of ordinary skill in the art will readily realize the conventional computer system 10 may use a higher amount of power than desired. For certain operating systems and processors, such as the MICROSOFT™ operating system and certain INTEL™ processors, use of a USB device attached to a USB connector precludes the processor from entering a lowest power state, known as a C3 state. In other words, because of certain USB host implementations, if the operating system for the host 12 detects the presence of a USB device then the processor cannot enter its lowest power state. In the conventional computer system 10, and as required by USB specifications, the operating system in the host 12 considers the USB hub 16, which is integrated into the conventional computer system 10, to be a USB device. Consequently, a USB device is always detected, even when no external USB devices are utilized. As a result, processors in the host 12 will never be able to enter the lowest power state. The conventional computer system 10 may, therefore, consume more power than is desirable. This is a particular problem if the conventional computer system 10 is a computer system, such as a notebook, that has a mobile mode. In such a computer system, the power supply 22 includes a battery for supplying power to the conventional computer system 10 when in mobile mode. When in the mobile mode, it is desirable to allow the host 12 to enter a lowest power state in order to conserve battery power, for example when the host 12 is not actively being used. Because the processors in the host 12 cannot enter the lowest power state, the battery will discharge more rapidly. The battery may lose its charge, preventing the user from utilizing the conventional computer system 10 when desired.
Accordingly, what is needed is a system and method for providing a system that allows a computer system having a USB hub to manage power. The present invention addresses such a need.